Role Of MgO Research Articles

Role of MgO in Al2O3‐supported Fe catalysts for hydrogen and carbon nanotubes formation during catalytic methane decomposition

AbstractCatalytic methane decomposition is a promising technology for reducing the reliance on fossil fuels and mitigating the effects of climate change by producing clean hydrogen and value‐added carbon without the emission of greenhouse gases. The aim of the study was to investigate the use of Al2O3‐modified MgO doped iron‐based catalysts for the catalytic decomposition of methane. The catalysts were synthesized using the impregnation method and characterized using various analysis techniques, including Brunauer, Emmett, and Teller, temperature programmed reduction, temperature programmed oxidation, X‐ray diffraction, thermal gravimetric analysis, Raman, scanning electron microscopy, and transmission electron microscopy. The activity of the synthesized catalysts was tested in a packed‐bed reactor with a gas flow rate of 20 mL/min at a temperature of 800°C. The investigation focuses on the influence of incorporating magnesium into alumina catalysts with MgO concentration ranging from (20%–70%), where higher magnesium levels improve catalytic activity by creating more active sites, positively impacting methane decomposition. Enhanced catalyst reducibility and increased particle dispersion lead to improved catalytic properties despite the reduced surface area. The FA70M and FA63M catalysts exhibited almost the same catalytic characteristics and the highest stability and methane conversion among the catalysts investigated, reaching 87% and 85% at 800°C for 120 min. Moreover, both catalysts showed hydrogen yields of 86% and 85%, respectively. The introduction of MgO further increased the total carbon yield from 103% with FA and 39% for FM to 114% and 120% for the respective catalysts (FA70M and FA63M). During the methane decomposition reaction, carbon nanotubes of varying diameters were produced. Higher iron loading resulted in a positive trend.

The role of MgO on physical and bioactive properties of borophosphate glasses for biomedical applications

In this work, a novel series of borophosphate glasses of the system 40B2O3–25P2O5–(20-x)Na2O–15CaF2–xMgO (x = 0, 2.5, 5, 7.5, and 10 mol%) were synthesized using the melt-quenching technique. The effect of replacing Na2O with MgO in the glasses was analyzed by the physical and bioactive properties. The glasses were characterized by density, molar volume, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Differential thermal analysis (DTA), bioactivity tests in simulated body fluid (SBF), pH measurements, mass loss, and verification of cellular compatibility in RAW 247 murine macrophages. XRD and FTIR analyses were performed before and after immersion in SBF to verify the bioactivity. Density, molar volume and FTIR results before SBF showed structural changes in the glasses due to the addition of MgO. The pH and mass loss measurements allowed to verify the degradation behavior of the glass series as a function of MgO concentration. The DTA data showed an increase in Tg, Tx, and thermal stability due to the increase in MgO addition. XRD and FTIR analyses after SBF soaking showed superficial formation of apatites and other calcium phosphates of biological interest in the samples, attesting the bioactivity. Cytotoxicity assessed by MTT assay on the cell line RAW 247 showed that at a concentration of 500 μg/mL all glasses were compatible (non-cytotoxic). The results suggest that the synthesized glasses are bioactive, with the sample containing 5 mol% MgO exhibiting the bioactivity and biocompatibility required for biomaterial applications.

Evaluation of MgO as a promoter for the hydrogenation of CO2 to long-chain hydrocarbons over Fe-based catalysts

Thermocatalytic conversion of CO2 into liquid fuels and chemicals is a promising approach to mitigate global warming. Although, the CO2 conversion and long-chain hydrocarbon selectivity are highly dependent on the choice of metal-oxide promoter, but role of the promoter remains unclear. Herein, the role of MgO as a promoter for an Fe-based catalyst was investigated. Bimetallic Na-FeMgOx catalyst exhibited a high C5+ yield of 25.1% with a CO2 conversion of 49.1% at the early stage of the reaction. The presence of MgO facilitates the reduction of Fe oxides and formation of oxygen vacancies by transferring electrons to Fe-based phases. In addition, at the early stage of reaction, the decoration of the Mg oxide surface with nanosized χ-Fe5C2 enhances the C5+ yield. However, the progressive transformation of MgO to MgCO3 during CO2 conversion deactivates the Na-FeMgOx catalyst. A detailed deactivation mechanism is also discussed.

The role of MgO during CO2 hydrogenation to methanol over Pd/ZnO catalyst

The role of MgO during CO2 hydrogenation to methanol over Pd/ZnO catalyst

MgO Heterostructures: From Synthesis to Applications.

The energy storage capacity of batteries and supercapacitors has seen rising demand and problems as large-scale energy storage systems and electric gadgets have become more widely adopted. With the development of nano-scale materials, the electrodes of these devices have changed dramatically. Heterostructure materials have gained increased interest as next-generation materials due to their unique interfaces, resilient structures and synergistic effects, providing the capacity to improve energy/power outputs and battery longevity. This review focuses on the role of MgO in heterostructured magnetic and energy storage devices and their applications and synthetic strategies. The role of metal oxides in manufacturing heterostructures has received much attention, especially MgO. Heterostructures have stronger interactions between tightly packed interfaces and perform better than single structures. Due to their typical physical and chemical properties, MgO heterostructures have made a breakthrough in energy storage. In perpendicularly magnetized heterostructures, the MgO’s thickness significantly affects the magnetic properties, which is good news for the next generation of high-speed magnetic storage devices.

Study on the Catalytic Decomposition Reaction of N2O on MgO (100) in SO2 and CO Environments

To study the role of MgO in the reduction of N2O in circulating fluidized bed boilers, density functional theory was used to evaluate heterogeneous decomposition. The interference of SO2 and CO on N2O was considered. N2O on MgO (100) is a two-step process that includes O transfer and surface recovery processes. The O transfer process is the rate-determining step with barrier energy of 1.601 eV, while for the Langmuir–Hinshelwood and Eley–Rideal surface recovery mechanisms, the barrier energies are 0.840 eV and 1.502 eV, respectively. SO2 has a stronger interaction with the surface-active O site than that of N2O. SO2 will occupy the active site and hinder N2O decomposition. CO cannot improve the catalysis of MgO (100) for N2O because O transfer is the rate-determining step. Compared with homogeneous reduction by CO, MgO has a limited catalytic effect on N2O, where the barrier energy decreases from 1.691 eV to 1.601 eV.

Role of MgO in lowering glass transition temperature and increasing hardness of lithium silicate glass and glass-ceramics

The effect of variation of MgO (1.5, 4.5 and 7.5 mol%) content on glass structure, crystallization behavior, microstructure and mechanical properties in a Li2O–K2O–Na2O–CaO–MgO–ZrO2–Al2O3–P2O5–SiO2 glass system has been reported here. Increased amount of MgO enhanced the participation of Al2O3 as a glass network former along with [SiO4] tetrahedra, reducing the amount of non-bridging oxygen (NBO) and increasing bridging oxygen (BO) amount in glass. The increased BO in glass resulted in a polymerized glass structure which suppressed the crystallization and subsequently increased the crystallization temperature, bulk density, nano hardness, elastic modulus in the glasses as well as the corresponding glass-ceramics. MgO addition caused phase separation in higher MgO (7.5 mol%) containing glass system which resulted in larger crystals. The nano hardness (∼10 GPa) and elastic modulus (∼127 GPa) values were found to be on a much higher side in 7.5 mol% MgO containing glass-ceramics as compared to lower MgO containing glass-ceramics.

The Role of Mgo Supported Sodium Sulfate Molten Salt for Calcium Looping Thermochemical Energy Storage

The Role of Mgo Supported Sodium Sulfate Molten Salt for Calcium Looping Thermochemical Energy Storage

Enhanced activity and stability of MgO-promoted Ni/Al2O3 catalyst for dry reforming of methane: Role of MgO

Highly dispersed nickel nanoparticles (NPs) were deposited on Al2O3 NPs by atomic layer deposition (ALD). Various amounts of MgO were loaded on Ni/Al2O3 catalysts by the incipient wetness (IW) method for dry reforming of methane. Fresh and used catalysts were systematically characterized to reveal the effects of MgO on the catalytic performance. MgO was found to increase the basic amount and basic strength of catalyst surfaces, which provided additional surface oxygen species and assisted the adsorption and activation of CO2. Although the formation of NiO-MgO solid solution, during the calcination of incipient wetness, did not improve the overall reducibility, the Ni NPs from NiO-MgO solid solution after reduction formed an intimate interaction with MgO, which could inhibit Ni NPs from sintering and provide sufficient metal-support interface for CO2 activation. The MgO-promoted Ni/Al2O3 reached a methane reforming rate of 1780 LCH4gNi−1 h−1 at 850 °C, which is 26% more than that of the pristine Ni/Al2O3. The higher CO2 activity enhanced the oxidation rate of the surface carbon generated from side-reactions, thereby resulting in a higher reforming rate and inhibiting coke formation, especially the detrimental graphitic encapsulating carbon on the active nickel surface.

The reaction kinetics of CO2 methanation on a bifunctional Ni/MgO catalyst

A bifunctional Ni/MgO catalyst was prepared to catalyze CO2 methanation and make use of CO2 as an abundant hydrogen storage facility. The effect of Ni loading and MgO quality on the rate of methanation was tested in a temperature range of 533–648K. The Ni loading was varied between 0 to 27wt.% on MgO. To investigate the impact of matrix elements, a MgO/CaO support was tested with 21wt.% nickel loading. Further, the role of MgO in the bifunctional catalyst was proven. The reaction kinetics was modeled with a Langmuir–Hinshelwood approach considering the bifunctional character of the catalyst. Nickel provides the adsorbent capacity for hydrogen and is highly selective for methane. MgO activates CO2 through chemisorption. Increasing Ni loading of the catalyst increased the rate of CO2 conversion. According to the results, the mechanism of CO2 methanation did not change with Ni loading. The Ni/MgO catalyst acted as a robust, active and highly selective catalyst for CO2 methanation. With CO2 conversion of 87%, the selectivity to methane was ≥99%. Besides excellent catalytic activity the catalysts suffice the necessity of simple catalyst preparation, usage and recyclability for industrial applicability of CO2 methanation.

Role of MgO on densification and mechanical properties in spark plasma sintered Os0.9Re0.1B2 ceramic

To promote the densification and therefore the mechanical properties of boride-based ceramics, MgO was added as sintering aid into Os0.9Re0.1B2 powders for densification by using spark plasma sintering (SPS). The Os0.9Re0.1B2 powders were synthesized by mechanochemical method from powder mixture of Os, Re and amorphous B. The role of MgO on densification, phase composition, microstructure and mechanical properties (hardness, fracture toughness and wear behavior) were studied by using X-ray diffraction (XRD), scanning electron microscope (SEM) with energy-dispersive spectroscopy (EDS), micro indentation and ball-on-disk tribometer. The results show that, with the introduction of MgO as sintering aid, the relative density of the Os0.9Re0.1B2 ceramic samples increased. When the MgO content reached 9 wt%, the as-sintered sample is almost fully dense. No obvious regularity was found from the samples with the addition of different content of MgO. Vickers hardness values of the samples with 0, 3 wt% and 9 wt% MgO are found to be very close with each other within the experimental error (~30 GPa), while the sample with the addition of 6 wt% MgO exhibits the highest hardness of ~35 GPa. The fracture toughness of the samples is decreased slightly with the addition of MgO. The friction coefficient and wear rate of the sample with the addition of 6 wt% MgO was also found to be the lowest among all samples, which indicate best wear resistance. As a whole, with the addition content of 6 wt% MgO, the Os0.9Re0.1B2 ceramic sample performs relatively excellent mechanical properties among four groups of samples.

The Role of MgO as Swelling Cements Admixtures under CO2 Attack on API Class-G Cement

API Class-G Portland cement commonly put in as zonal isolation material in oil and/or gas well. Corrosion against the well zonal isolation material could lead to potential leakage of formation fluid such oil, gas, or water. It is widely known that ordinary Portland cement is thermodinamically unstable in CO2 rich environment, which can be found in the CO2 geological sequestration. CO2 attack on API Class-G cement had been observed through experiments that simulate the down hole condition of Geological Sequestration of CO2. Some of the experiment reveal the detrimental effect of CO2 such as increase of porosity and permeability of cement sheath corroded by CO2 attack. The degradation of API Class-G cement by CO2 involves emergence and crystallization of CaCO3 from Ca(OH)2 which is formed during hydration of cement. In this experiment, we examine the role of addition of MgO swelling cement by weight fraction to mitigate the corrosion caused by CO2 against downhole hardened API Class-G cement thus inhibits the occurrence of leakage path of CO2. Observation for characterization and analysis by XRD, optical microscope, and cement paste uniaxial volumetric expansion presented in this paper. The conclusion will provide insights into design of carbonation resistant cement slurries using swelling cements admixtures.

The Role of MgO and CaO Nano-Particles on Staphylococcus Epidermidis Isolated from Catheter Indwelling Patients

The Role of MgO and CaO Nano-Particles on Staphylococcus Epidermidis Isolated from Catheter Indwelling Patients

Methane steam reforming at low temperature over Ni-MgO-Al2O3 catalysts: activity and resistance to coking

<p>The role of MgO as a factor improving the resistance to coking of the alumina supported nickel catalysts in the steam reforming of hydrocarbons is discussed. A series of catalysts containing variable amounts of MgO, NiO and a constant amount of Al<sub>2</sub>O<sub>3</sub> was prepared by the co-precipitation method. It was found that the specific activity of the catalysts exhibits a broad but not deep minimum for the MgO contents from 8.5 to 27.3 wt.%. At the same time these catalysts reveal a high resistance to coking either in the reaction with methane or with <em>n</em>-butane. The most promising composition, in terms of the activity and simultaneous resistance to the coke formation, was found to be 27.3 wt.% of MgO and 39.0 wt.% of NiO. The analysis of various factors controlling the activity and resistance to coking leads to the conclusion that MgO reduces the catalysts acidity what, in consequence, reduces the rate of coke formation during the reforming reactions. Furthermore, The resistance to coking correlates well with the mean size of nickel crystallites, the same is observed for the specific catalyst activity.</p><p> </p>

Effect of the Addition of CeO2 or MgO on the Oxygen Carrier Capacity and Rate of Redox Reactions of NiO/Fe2O3/Al2O3 Oxygen Carriers.

Two compositions of mixed oxygen carriers (OCs), N1F1A1 (mole ratio of NiO to Fe2O3 is 1:1) and N1F2 (mole ratio of NiO to Fe2O3 is 1:2), were fabricated by mechanical mixing, and the effects of CeO2 and MgO additives on the oxygen-transfer capacity (OTC) and crystal structure were analyzed. In addition, X-ray diffractometry after the oxidation and the reduction steps was carried out to determine the reaction mechanism. Potential mixed OCs of the candidates of various OCs, such as NiO/Fe2O3, are proposed based on the OTC and oxygen-transfer rate evaluated via X-ray diffraction (XRD) phase analysis and thermogravimetric analysis. The chemical reaction equation for the oxidation and reduction was suggested based on the XRD characterization of the phases including NiFe2O4 and MgAl2O4 in N1F1A1 (①) and N1F1A1-Mg5 (④). Addition of MgO is confirmed to enhance the OTC and oxygen-transfer rate. The mechanism of the oxidation and reduction of metal oxides and the role of MgO were suggested. Even though the addition of MgO does not transfer oxygen to the fuel, it does accelerate the oxidation and reduction reactions of NiFe2O4.

Role of MgO in Sinter from Perspective of MgO Distribution between Liquid and Magnetite Phases in FeO<sub>x</sub>–CaO–SiO<sub>2</sub>–MgO System

Role of MgO in Sinter from Perspective of MgO Distribution between Liquid and Magnetite Phases in FeO<sub>x</sub>–CaO–SiO<sub>2</sub>–MgO System

The role of MgO in the performance of Pd/SiO2/cordierite monolith catalyst for the hydrogenation of 2-ethyl-anthraquinone

Highly dispersed Pd/SiO2/cordierite monolith catalysts (PSC) were prepared to investigate the influence of support alkalinity on 2-ethyl-anthraquinone (eAQ) hydrogenation. The support alkalinity was adjusted by the MgO content in SiO2 washcoat. The behavior of the PSC catalysts was tested by liquid phase hydrogenation of eAQ in a continuous trickle bed reactor. PSC catalyst with 2wt.% MgO (Mg-2 sample) exhibited excellent for hydrogenation of eAQ. The support alkalinity directly influenced the electronic properties of the Pd nanoparticles as proved by Fourier transformed infrared spectroscopy with CO probe molecule and X-ray photoelectron spectroscopy. The electron density at lower binding energy of the supported Pd particles increased with the increasing alkalinity. PSC catalysts with alkali modifiers exhibited higher hydrogenation efficiency for benefiting the activation of CO group in eAQ and the adsorption of eAQ via the enhanced interaction of lone pair of CO electrons. However, increased support alkalinity contributed to higher Pd loss due to the weak coating strength. Besides, the active quinone selectivity decreased with the progressive MgO addition due to the tautomerization of 2-ethylanthrahydroquinone to 2-ethyloxoanthrone, which is the precursor of other degradations. Consequently, a volcano shape curve between hydrogenation efficiency (H2O2 yield) and MgO content was obtained.

Role of MgO over γ-Al2O3-supported Pd catalysts for carbon dioxide reforming of methane

A series of Pd/Al2O3 catalysts with varying Mg loading (1, 3, 7 and 10wt%) were investigated for carbon dioxide reforming of methane. It was observed that the initial catalytic activities and long-term stabilities in terms of both CO2 and CH4 conversions increased with increasing Mg content when its loading was below 7wt%. When Mg content was up to 10wt%, the initial activity and stability decreased. Moreover, Pd7Mg/Al2O3 displayed the highest H2 and CO yields. Characterization results conducted on catalysts before and after reaction test demonstrated that MgO mainly presented in amorphous form for catalysts with additive content below 7wt%; while a fraction of MgO transformed into crystalline form when more additive was introduced to the catalyst. The amorphous MgO significantly enhanced surface metal dispersion, decreased average Pd crystallite size and thus improved resistances against both metal sintering and carbon deposition, which contributed to the enhanced initial activities and long-term stabilities. On the contrary, the crystalline MgO decreased exposed Pd active sites, caused metal sintering and thus led to increased amount of carbon deposition owing to both its negative decoration effect on surface metal and deterioration effect on textural characteristics of support. These factors were responsible for the worse catalytic performance of Pd10Mg/Al2O3 as compared to that of Pd7Mg/Al2O3.

Effects of MgO addition on sintering of calcium phosphate ceramics and composites

Bioactive ceramics attracts much attention as materials for bone implants, because of their high biocompatibility. For example, hydroxyapatite (HA) has bone-bonding ability through a bone-like apatite layer in body environment and β-tricalcium phosphate (β-TCP) has a high bioresorbability in body environment. In addition, HA/β-TCP composites has the characteristics of both HA and TCP. However, it is difficult to sinter the composite, so that MgO has been used as a sintering agent. In the present study, effects of MgO addition on sintering calcium phosphate ceramics and composites were investigated. In order to evaluate the effect of MgO on the composites, HA, HA/β-TCP(30wt%), and HA/β-TCP(50wt%) with 1wt% MgO were prepared and characterized. To clarify the role of MgO on sintering of calcium phosphate ceramics, HA, β-TCP, and α-TCP with different TCP content (0, 1, 2, 3, 4, and 5 wt%) were also prepared. The results suggest that MgO addition densified HA/β-TCP composites and gave higher strength composites. The results of monolithic calcium phosphate ceramics indicated MgO addition was effective on β-TCP and α-TCP, not on HA. The maximum content of Ca atom in β-TCP displaced with Mg atoms in MgO might be 24 atm%.

Barium Borosilicate Sealing Glasses Synthesized by a Sol–Gel Process: Chemical Interactions with a Stainless Steel and Gas‐Tightness of a SOFC

AbstractSeveral glasses synthesized by sol–gel route and based on the BaO–B2O3–X–Al2O3–SiO2 (X = CaO, MgO) glass system have been investigated to evaluate their applicability as sealant for solid oxide fuel cell (SOFC). Chemical interactions with K41X stainless steel and hydrogen‐tightness of these materials were evaluated after operations at high temperatures over 1,000 h in air atmosphere. Formation of a new phase at the steel–glass interface and formation of porosity in the glass were observed and determined as critical problems over mid‐term operations. The role of MgO is important to obtain a gas‐tight sealing. Application of the glass paste without binder addition was performed in order to avoid possible residual porosity related problems. The best glass was finally used as sealant between anodic and cathodic compartments in complete SOFCs operated at 760 and at 800 °C. Open circuit voltages and power densities of the cells were recorded during the first hours of operation.